Question answering (QA) is the task of automatically answering a question posed in natural language. At this time, there exists several QA approaches, and, according to recent evaluation results, most of them are complementary. Some of them use the evolutionary algorithms, such as the genetic algorithm, in itself. In this paper we propose a question answering system that uses the artificial immune algorithms, for searching in the knowledge base to find the right answer. This algorithm is one of the evolutionary algorithms. Search is based on two features: (i) the compatibility between question and answer types, (ii) the overlap and non-overlap information between the question-answer pair. Experimental results are encouraging; they indicate significant increases in the accuracy of proposed system, in comparison with the previous systems.